1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a facsimile and a printer.
2. Description of the Related Art
As shown in FIG. 4, a conventional image forming apparatus has the driving unit 48 including a plurality of motors 43 to 45 for driving a plurality of photosensitive drums. The driving unit 48 can be attached to and removed from the base frame 47c of the main body of the image forming apparatus.
The driving unit 48 has the front frame 41 and the rear frame 42 which faces the front frame 41. All the motors 43 to 45 of the driving unit 48 are mounted on the rear frame 42. Any motor is not mounted on the front frame 41. In such a configuration, a problem arises where vibration generated by the motors 43 to 45 is transmitted to the rear frame 42 and a radiation sound is generated from the rear frame 42 and the radiation sound is emitted to the outside of the apparatus, thereby increasing noise.
In Japanese Patent Laid-Open No. 2000-235396, noise reduction is intended by designing the apparatus such that the exterior member constitutes a Helmholtz resonator. In addition, there are some configurations where noise reduction is intended by making an exterior member to be a laminated body in which a solid layer and an air layer are alternately laminated, or to be a hollow double-walled structure.
However, in the conventional configurations for achieving noise reduction by an exterior member, a design thereof is complicated and an apparatus becomes large.
Therefore, as shown in Japanese Patent Laid-Open No. 2009-282122, it is conceived to distribute a plurality of motors for driving photosensitive drums to different supporting plates of the driving unit.
However, when such a configuration is employed, the following problem occurs. The positions of supporting plates are different with respect to the axial direction of the photosensitive drum. Therefore, positions of a plurality of motors mounted on the supporting plates are different from each other with respect to the axial direction of the photosensitive drums, and the positions of the gear trains for transmitting the driving force to the photosensitive drums are also different with respect to the axial direction of the photosensitive drums for each supporting plate to which each motor is attached. This necessitates a change of positions of drive input devices of the process cartridge for inputting force from the gear trains depending on the positions of the supporting plates on which the motors are mounted.